a) Field of the Invention
The present invention relates to an electron gun, and more particularly to an electron gun suitable for both increasing the energy of and raising a repetition frequency of an electron beam periodically emitted from the electron gun.
b) Description of the Related Art
A radio-frequency electron gun (RF gun) using a photocathode comprises a conductive chamber defining a cavity, a photocathode for emitting photoelectron into the cavity, and a wave guide for generating an RF electric field in the cavity. As light is periodically applied to the photocathode, photoelectrons are emitted into the cavity intermittently. These photoelectrons are converged and accelerated by the RF electric field generated in the cavity. The RF electric field is applied synchronously with application of light to the photocathode. For example, a repetition frequency of light application is set to about 10 Hz.
It has been desired to raise the repetition frequency of an electron beam periodically emitted from the electron gun. It has also been desired to increase the energy of the emitted electron beam.